This invention refers to the acclimation of truck cabins and could eventually be extended to other types of medium and long-distance freight transports, road building and agricultural machines and other means of locomotion. More particularly, it refers to an air cooler of the type which can be mounted on the roof of a cabin and is provided with an intake for external air to be cooled and circulated within the cabin.
Cooling is generally carried out by passing the air through a radiator/evaporator manufactured from a porous material which is kept moist, which fulfils the double function of a thermal exchanger, in taking heat from the air, and a moistener, which gives the sensation of the air having been cooled. The cabin is cooled by the lower temperature of the acclimated air and by the evaporation of moisture brought in with the air. This invention specifically refers to the moistening arrangement of the evaporator.
These cooler units are attractive due to their lower cost and maintenance compared with the traditional air conditioning units. Furthermore they do not consume power from the engine of the truck, which means operative economy in addition to not reducing the available power which the transport vehicle uses for its own locomotion. These coolers can also be adapted to other uses, such as transitory or precarious living quarters, for example, and workshops. The advantage in these static installations is that they avoid the use of compressors and electrical consumption.
Coolers of the type described in the previous section are known on the market. These units have a water reservoir and a pump that circulates the water towards the evaporator in order to keep it moist. An electric fan passes the air from the intake towards the interior of the cabin, passing the air through the evaporator, where the air is cooled, giving up heat and absorbing moisture.
These units are commercially successful due to their simplicity and the previously stated advantages. Argentina Patent No. 235,114 and U.S. Pat. No. 3,867,486 describe coolers with those features.
FIG. 1 schematically illustrates a typical cooler unit which reflects, in general, the features of Argentina Patent No. 235,114. It is made in a plastic housing 1 having a front panel in the form of an air intake grid 12. The air is sucked in through a tubular evaporator 7 with a porous side-wall, the cooled air leaving through a gorge 11 made in the base of the housing into the cabin, through an orifice made in the roof. The moistening water comes from an external reservoir 29 and is fed, by means of a pump 31 and an 8-mm diameter hose 6, to a coil 5 within the housing 1 which doses it onto the wall of the evaporator 7. The return water precipitates on the bottom of a gutter 14, where it is collected for returning to the reservoir 29 by means of a 13-mm diameter descending hose 15, one end of which is connected to the rear part of the cooler unit and the other end of which penetrates approximately 20 mm into the reservoir 29 through the top thereof.
Modern trucks are designed taking special care on the aerodynamics of their external shape, as they are faster than their predecessors and must economize fuel consumption. To this effect, the roofs of new cabins slope forwards and downwards, in order to enhance penetration and reduce drag. These modern lines mean that when mounting a cooler as the one previously mentioned, the cooler should also be inclined forwards, in line with the sloped roof.
A disadvantage in installing coolers in units with forwardly sloping roof-tops is returning the excess water collected from the evaporator gutter to the reservoir, since the gutter becomes inclined with the roof-top such that the return hose in the rear part is at a higher level than the gutter rather than permanently descending (see, for reference, the important note on page 11 of the installation manual of the VIESA cooler). Aesthetic reasons and interference with the external air intake discourage the alternative of placing the return hose such that it exits through the front of the cooler unit. In the case of U.S. Pat. No. 3,867,486, the reservoir is housed within the cooler housing; however, the problem subsists due to the fact that the recirculation hose is not connected to the lower part of the reservoir.
Therefore, installers currently have two viable options in order to solve this inconvenience. The first and simplest one is to raise the front part of the unit, which aerodynamically and aesthetically puts it out of line. The other option is to add a second pump in order to overcome the difference in level and pump the water back. This second solution implies the addition of another component, which affects the cost and maintenance, specially taking into account the fact that the attractiveness of these units lies in their simplicity and economy.
Therefore, an object of this invention is to resolve efficiently and aesthetically the problem of water return in cooler units installed on sloped cabin roofs.
Another object of the invention is to provide a water return system without additional pumps in coolers installed sloping downwards away from the return hose entry.
Another object of the invention is to enhance the circulation of the return water towards the rear part of the cooler without lifting up the front part of the cooler from its natural position along the line of the cabin roof.
This invention achieves these and other objects and advantages which will become apparent in the ensuing specification, in an ingenious manner by disconnecting the return hose from the top-wall of the water reservoir and reconnecting it to the outlet of the pump, in parallel with the feed hose which keeps the evaporator moist. The pump suitably operates intermittently on the basis of a predetermined duty cycle to maintain the evaporator wet within the practical limits of moisture. The diameter of the return hose, which is actually or effectively smaller than the diameter of the hose feeding the coil, is dimensioned so that each on-cycle of the pump will be enough to purge it with a minimal entry of water into the gutter.
Preferably, the duty cycle of the pump is lower than 10%, more preferably 1:12, approximately. In this way, in each on-cycle, the pump supplies a greater volume flow of water from the reservoir to the coil through the larger hose to moisten the evaporator efficiently and a lesser volume flow of water towards the gutter but sufficient to purge the smaller return hose, so that the former will siphon return water from the gutter towards the reservoir during the idle cycles of the pump.
In addition to solving the stated problem efficiently, this invention has the advantage that it does not require modification to the cooler and likewise is applicable to models of existing units by changing the return hose and its connection on one side of the reservoir.